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Data Set ID:
NSIDC-0121

Visible Stratigraphic Dating, Siple Dome and Upstream C Cores, Version 1

This data set is part of the West Antarctic Ice Sheet cores (WAISCORES) project, an NSF-funded project to understand the influence of the West Antarctic Ice Sheet on climate and sea level change. WAISCORES researchers acquired and analyzed ice cores from the Siple Dome, in the Siple Coast region, West Antarctica.

This data set includes melt layers and annual layer data for Siple Dome cores A through J, and upstream core C (UpC). Cores were examined on a light table after the core had been sectioned longitudinally and samples removed for isotopic, chemical, and other analyses, and after the surface had been smoothed using a planer. Major stratigraphic features were noted, such as coarse-grained and fine-grained firn at shallow depths, and coarse-bubbled and fine-bubbled ice at greater depth. Melt layers were identified as bubble-free or nearly-bubble-free zones. Core lengths ranged from 30 to 133 meters.

Data in this collection were obtained in the summer of 1997. The data set is available via FTP as ACSII data (.dat), metadata (.meta) and text (.txt) files.

Geographic Coverage

Spatial Coverage:
  • N: -81, S: -81, E: -149, W: -149

Spatial Resolution: Not Specified
Temporal Coverage:
  • 1 June 1997 to 31 August 1997
Temporal Resolution: Not specified
Parameter(s):
  • Glaciers/Ice Sheets > Glacier Thickness/Ice Sheet Thickness
  • Ice Core Records > Ice Core Air Bubbles
  • Ice Core Records
  • Snow/Ice > Ice Depth/Thickness
  • Glaciers/Ice Sheets > Ice Sheets
  • Ice Core Records > Isotopes
  • Snow/Ice > Snow Depth
  • Snow/Ice > Snow Stratigraphy
Platform(s) GROUND STATIONS, GROUND-BASED OBSERVATIONS
Sensor(s): CORING DEVICES
Data Format(s):
  • ASCII Text
Version: V1
Data Contributor(s): Richard Alley

Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Alley, R. 1997. Visible Stratigraphic Dating, Siple Dome and Upstream C Cores, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: http://dx.doi.org/10.7265/N53F4MHS. [Date Accessed].

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Detailed Data Description

This data set is part of the West Antarctic Ice Sheet cores (WAISCORES) project, an NSF-funded project to understand the influence of the West Antarctic Ice Sheet on climate and sea level change. WAISCORES researchers acquired and analyzed ice cores from the Siple Dome, in the Siple Coast region, West Antarctica.

This data set includes melt layers and annual layer data for Siple Dome cores A through J, and upstream core C (UpC). Cores were examined on a light table after the core had been sectioned longitudinally and samples removed for isotopic, chemical, and other analyses, and after the surface had been smoothed using a planer. Major stratigraphic features were noted, such as coarse-grained and fine-grained firn at shallow depths, and coarse-bubbled and fine-bubbled ice at greater depth. Melt layers were identified as bubble-free or nearly-bubble-free zones. Core lengths ranged from 30 to 133 meters.

Data in this collection were obtained in the summer of 1997.

Format

The data contains data (.dat), metadata (.meta), and text (.txt) files.

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File and Directory Structure

Data are available on the FTP site in the ftp://sidads.colorado.edu/pub/DATASETS/AGDC/waiscores/alley/ directory. Within this directory, there are a total of 21 files. Nineteen data files contain melt data and visible stratigraphic data information for Siple Dome ice cores A through J and Upstream core C (UpC). Two metadata files, psuvis.meta and psumelt.meta, contain researcher's notes on data processing for the two layer dating techniques.

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File Naming Convention

Files are named according to the following convention and as described in Table 1:
Note. Melt layer data for Siple Dome ice core A is listed in the file sdma_years.txt.

Example: psumeltb.dat and psuvisb.dat

Where:

Table 1. File Naming Convention
Variable Description
psu Pennsylvania State University
melt Melt data
vis Visual stratigraphy data
b Siple Dome ice core identification, in this case Siple Dome ice core B
.dat File extension
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File Size

Files in this data set range in size from 1KB to 194 KB.

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Volume

The entire data set is less than 500 KB.

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Spatial Coverage

Southernmost Latitude: -81°
Northernmost Latitude: -81°
Westernmost Longitude: -149° 
Easternmost Longitude: -149°

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Temporal Coverage

The data in this collection were collected and analyzed in 1997.

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Parameter or Variable

Parameter Description

This data set contains files with melt layer data and visual stratigraphy data for Siple Dome ice cores A-J and the Upstream C (UpC) Core.

Melt layer files, such as psumeltb.dat, include bottom age and depth, listed in the heading, and a list containing the following parameters:

Table 2. Melt Layer Data Parameters
Parameter Description
melt layer year Layer age in years counted from the surface
confidence
  • 0.5: Possible melt, but not both convincing and likely to be recognizable after >50% strain thinning;
  • 0.75: Probable melt, count in most applications;
  • 1: Melt, little or no doubt.
depth Meters from surface

Visual stratigraphy files, for example psuvisb.dat, contain two columns, described in Table 3:

Table 3. Visual Stratigraphy Data Parameters
Parameter Description
depth of annual layer Depth of layer in meters from surface
confidence
  • 3: Clear indication
  • 2: Fair indication
  • 1: Poor indication
  • 0.5: Something present, but not picked as a summer
  • 0: Interpolated where visible examination too difficult for choices, as in badly fractured or wafered core

Sample Data Record

Melt layer:

Melt Layer Year
Confidence
Depth
19
1
5.065

Visual stratigraphy:

Depth of annual layer (m)
Confidence
0.200
1
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Software and Tools

Software and Tools

Data can be accessed using standard spreadsheet software.

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Data Acquisition and Processing

Data Acquisition Methods

Melt Layers

Melt layers were identified as bubble-free or nearly-bubble-free zones. Ambiguity is introduced by thin crusts, which are approximately 1 mm thick, typically nearly uniform in thickness, and may result from multiple factors, including sun, drizzle, and wind packing. Crusts may occur in non-summer snow. To avoid counting crusts as melt layers, the researchers required that melt features be at least 2 mm thick. Ideally, melt features also show irregularity in thickness; in practice, thick features almost always do. Confidence levels were assigned as described in Table 2. For more information on melt layer data acquisition methods, see the researchers' notes in the file psumelt.meta.

Visual Stratigraphy

Ice cores were examined on a light table over fluorescent tubes. Visible examination occurred after the core had been sectioned longitudinally and samples removed for isotopic, chemical, and other analyses, and after the surface had been smoothed using a planer and then sampled electrically by Kendrick Taylor and other scientists. All core sections were transferred to core trays of clear plastic designed and built by the National Ice Core Laboratory (NICL), which has a curved cross-sectional aspect that conforms closely to the exterior of the core. For more information on visual stratigraphy data acquisition methods, see the researchers' notes in the file psuvis.meta.

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References and Related Publications

Contacts and Acknowledgments

Richard Alley 
Pennsylvania State University
306 Deike Building City: 
University Park Province, PA 16802

Acknowledgements: 

This research was supported by NSF OPP grant 9526374.

Document Information

DOCUMENT CREATION DATE

11 March 2009

DOCUMENT REVISION DATE

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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